The present invention relates to a method for the generation of a nearly monodispersed aerosol in filter-testing penetrometer machines.
The present invention is superior to the previous process in that it employs a candidate mixture as a replacement for dioctyl phthalate (DOP), which is a suspected carcinogen. In the following discussion, the term "Candidate Material" will be used to designate an aerosol mixture containing in percentage, by volume, of about 60-66 isosteric acid, 13-17% of isooleic acid, 1-3% of isopalmitic acid, 8-10% stearic acid, and 6-12% of oleic acid. The candidate mixture is manufactured by Henkel Corporation, Emery Group, 11501 Northlake Drive, P.O. Box 429667, Cincinnati, Ohio 45249. The candidate mixture has been identified by us as a thermally stable material of low toxicity.
For several decades, the U.S. Army has produced hot smokes using DOP as the standard material in the performance of nondestructive gas mask and filter serviceability testing. Hot smokes are aerosols produced using a method of thermally-generated vaporization and recondensation (self nucleation) of particles. Heated air passes across the surface of a heated liquid (DOP); cooler air then merges with the vapor causing recondensation of an aerosol or "hot smoke." The U.S. Army Surgeon General has designated DOP as a suspected carcinogen and has prohibited or severely restricted its use in smoke-generating machines used to test U.S. Army masks, respirators, filters, and other personnel protection equipment.
The ATI model TDA-100 (Q-127) monodispersed filter penetrometer is manufactured by Air Techniques, Inc. (ATI), a Division of Hamilton Associates, Inc., 1718 Whitehead Road, Baltimore, Md. 21207. A description of this equipment is given elsewhere in this disclosure. Thus, the candidate material and process have been shown to be acceptable to the manufacturer for specification in his new machines.